This application claims the benefit of Korean Application Nos. 99-48452, filed Nov. 3, 1999 and 00-15328, filed Mar. 25, 2000, in the Korean Patent Office, the disclosures of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to optical recording/playback, and more particularly, to a physical identification data (PID) addressing method using a wobble signal, a wobble address encoding circuit, a method and circuit for detecting the wobble address, and a recording medium in a high density optical recording and reproducing system.
2. Description of the Related Art
Information used for physical location recognition to determine a location to which data is written on a disc in an optical recording and reproducing system is referred to as physical identification data (PID). Generally, PID is address information of a physical sector in a recording and reproducing medium on which data is recorded in units of sectors. This is essential information for recording data at a certain location on a disc and finding the location at a later time.
In other words, PID indicates address information for finding a specified sector to record/reproduce data to/from a certain location, particularly in a recording and reproducing disc, and indicates address information of a sector which is pre-mastered during manufacture of a disc regardless of existence or non-existence of user data. Accordingly, PID is supposed to be resistant to errors and have a structure allowing fast detection in order to exactly and quickly find the location of a sector which data will be recorded on or reproduced from.
Various methods of recording PID on a disc can be largely classified into two methods. One method is recording physical location information on a disc by forming embossed pits as used in a read-only optical disc to allow a certain location on the disc to be detected based on the embossed pits. The other method uses a wobble signal which can be obtained by giving some changes to recording tracks on a disc at a predetermined time interval.
An area, which is provided for performing PID addressing using the former method, that is, using embossed pre-pits, is referred to as a header field, as shown in FIG. 1. According to a digital versatile disc (DVD) specification for rewritable disc (2.6 or 4.7 gigabytes (GB) DVD-random access memory (RAM)) version 1.0, physical location information is recorded at the location of the so called header field, which comprises pre-pits, during manufacture of a substrate. The header field includes a variable frequency oscillator (VFO) area for a phase locked loop (PLL), a PID area to which a sector number is assigned, an ID error detection (IED) area for storing ID error detection information and a postamble (PA) area for setting up an initial state for modulation of data recorded following the header field. In a PID addressing method using pre-pits, such a header field comprising embossed pre-pits is appropriately disposed at the start of a sector to allow a pickup to easily find and move to a desired location using this information. A sector number, sector type and a land track/groove track can be recognized from the addressed information, and even servo control is possible.
In such a PID addressing method using conventional embossed pre-pits, data cannot be recorded in areas in which pits are formed. Therefore, a problem of a decrease in recording density in proportion to the areas where the pits are formed occurs.
To store a large amount of data with a high density, it is necessary to increase a recordable area (a user data area) by decreasing a track pitch and minimizing a non-recordable area (overhead). For this purpose, it is effective to use a wobble signal.
When forming a substrate for a recording disc, grooves are formed along recording tracks on the substrate to allow a certain track to be exactly tracked by a pickup even if data is not recorded on the track. The portions other than the grooves are referred to as lands. Recording methods can be classified into a method of recording data on either a land or a groove and a method of recording data on both the land and the groove. It is more advantageous to use the land and the groove recording method in which data is recorded on both the land and the groove as the density of data increases.
In addition, a method of generating a signal of a specified frequency by varying both walls of a groove to use it as an auxiliary clock signal during recording is used. This signal is referred to as a wobble signal. A wobble signal having a single frequency is also recorded in the substrate of a DVD-RAM disc.
In a PID addressing method using a wobble signal, overhead information such as a PID signal can be recorded by varying a wobble signal having a single frequency, for example, periodically varying the phase or frequency of the wobble signal, during recording. Here, the PID signal embedded in the wobble signal is generally referred to as a wobble address.
Since the conventional PID addressing method using a wobble signal uses the variation of both walls of a groove track in which a wobble will be recorded, as shown in FIG. 2, the method can be used only in discs employing a land recording method in which information is not recorded in groove tracks. In other words, when using changes in both walls of each groove track, address information of two groove tracks at both sides of a land track can be mixed with each other, so that exact information cannot be obtained from the land track. Accordingly, both the addresses of a land track and a groove track cannot be indicated just by using a wobble address formed in the groove track. Therefore, it is difficult to use the conventional method in discs employing a land and groove recording method in which information is recorded in both land and groove tracks.
Although a wobble address is recorded in the side wall of a groove track at the boundary between a land track and the groove track, information of wobbles formed in both walls of the land and groove tracks is simultaneously read when the land and groove recording method of recording information in land and groove tracks is used. Accordingly, a PID signal cannot be exactly recorded or detected when using the wobble addressing method shown in FIG. 2.
To solve this problem, a method of recording a wobble address in only one wall of each groove track is proposed, as shown in FIG. 3. In this wobble addressing method, however, since a wobble signal is generated from only one sidewall of a groove track, the strength of the signal decreases. In addition, since the same signal is read from the groove track and an adjacent land track, additional information for discriminating a land track from a groove track is required.
To solve the above problems, a first object of the present invention is to provide a new physical identification data (PID) addressing method using a wobble to solve an overhead problem of an addressing method using embossed pre-pits, and to solve a problem of a conventional wobble addressing method being incompatible with a land and groove recording method.
A second object of the present invention is to provide a method of addressing a PID using variation in either wall of a groove track or a land track such that a bi-phase shift keying (BPSK) signal is obtained in a groove track by phase modulating an address signal using the phase difference between wobbles of adjacent groove tracks, and a quadrature phase shift keying signal is obtained by summing the address signals of the adjacent two groove tracks.
A third object of the present invention is to provide a method of detecting address information from a recording medium in which address information indicating physical identification information is phase modulated in a groove track (or land track) using a wobble having a predetermined phase difference to a wobble formed in an adjacent groove track.
A fourth object of the present invention is to provide a wobble address encoding circuit for a high density optical disc recording and reproducing system.
A fifth object of the present invention is to provide a wobble address detecting circuit for a high density optical disc recording and reproducing system.
A sixth object of the present invention is to provide a recording medium in which address information indicating physical identification information is phase modulated in a groove track (or land track) using a wobble having a predetermined phase difference to a wobble formed in an adjacent groove track.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above objects, the present invention provides a method of addressing physical identification information using wobble signals on an optical recording medium. The method includes phase modulating wobble address information indicating the physical identification information using the wobble signals and recording the phase modulated wobble address information in either of a groove track and a land track, wherein the wobble address information is recorded using the wobble signals having a predetermined phase relation so that the wobble address information can be read from a track in which the wobble address information is not recorded.
The present invention also provides a method of detecting a wobble address from an optical recording and reproducing medium, in which wobble address information indicating physical identification information is phase modulated using wobble signals having a predetermined phase relation and recorded in either a groove track or a land track, in an optical recording and reproducing system having an optical detecting device. The method includes providing first and second output signals, each having an original signal and a harmonic component, by multiplying the difference signal between radially half-divided detection signals of the optical detecting device by the wobble signals having the predetermined phase relation, respectively; and removing the harmonic component from the first and second output signals and recovering groove address information and land address information from the original signals.
The present invention also provides a circuit for encoding an address using a wobble in an optical recording and reproducing system. The circuit includes a provider which provides a first wobble signal and a second wobble signal which has a predetermined phase relation with the first wobble signal, and a phase modulator which phase modulates address information indicating physical identification information using the first wobble signal with respect to one of adjacent odd and even tracks, which are defined by classifying groove tracks or land tracks into odd tracks and even tracks, and phase modulates address information using the second wobble signal with respect to the other track.
The present invention also provides a circuit for detecting a wobble address from an optical recording medium, in which wobble address information indicating physical identification information is phase modulated using wobble signals having a predetermined phase relation between adjacent even and odd tracks, which are defined by classifying groove tracks or land tracks into odd tracks and even tracks, and recorded in either a groove track or a land track, in an optical recording and reproducing system having an optical detecting device. The circuit includes a wobble clock recoverer which detects a first wobble clock signal using a difference signal (the push-pull signal) between radially half-divided detection signals of the optical detecting device and providing a second wobble clock signal having the predetermined phase relation with the detected first wobble clock signal; and a phase demodulator which recovers address information from the push-pull signal using the first and second wobble clock signals.
The present invention also provides a recording medium employing a groove/land recording method. The recording medium includes groove tracks classified into odd tracks and even tracks in which wobble address information indicating physical identification information is phase modulated using wobble signals having a predetermined phase relation, and recorded, and land tracks having quadrature phase shift keying (QPSK)-modulated wobble address information obtained from the wobble address information of two adjacent groove tracks.